Fabrication of carbon/SiO2 composites from the hydrothermal carbonization process of polysaccharide and their adsorption performance.

Abstract In this work, carbon/SiO 2 composites, using amylose and tetraethyl orthosilicate (TEOS) as raw materials, were successfully prepared by a facial hydrothermal carbonization process. The carbon/SiO 2 composites were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), Energy Dispersive Spectroscopy (EDS), transmission electron microscope (TEM), N 2 adsorption and Thermogravimetric (TG) analysis. The composites, which were made up of amorphous SiO 2 and amorphous carbon, were found to have hierarchical porous structures. The mass ratios of amylose and SiO 2 and the hydrothermal carbonization time had significant effects on the morphology of the composites, which had three shapes including monodispersed spheres, porous pieces and the nano-fibers combined with nano-spheres structures. The adsorption performance of the composites was studied using Pb 2+ as simulated contaminants from water. When the mass ratio of amylose and SiO 2 was 9/1, the hydrothermal time was 30 h and the hydrothermal temperature was 180 °C, the adsorption capacity of the composites achieved to 52 mg/g. Experimental data show that adsorption kinetics of the carbon/SiO 2 composites can be fitted well by the Elovich model, while the isothermal data can be perfectly described by the Langmuir adsorption model and Freundlich adsorption model. The maximum adsorption capacity of the carbon/SiO 2 composites is 56.18 mg g −1 .